Potassium Ferrocyanide uses in photography?

[Anon Ymous]

Yes, ferrocyanide, the yellow stuff. As far as I know, it doesn't have any uses in photography, but then I saw an ebay listing for it from a seller who only sells photographic chemicals. So, am I missing something?

 

[David Allen]

Perhaps what you saw was Potassium Ferricyanide?

This, when combined with Sodium Thiosulfate (plain hypo), creates Farmer’ s Reducer. This is a reducer that dissolves away the silver that forms the image in a print. This results in the area of the print that has been treated becoming progressively lighter.

Bests,

David.
www.dsallen.de

 

[Anon Ymous]

Perhaps what you saw was Potassium Ferricyanide?

Nope, he explicitly mentions that it was the yellow powder and even includes a photo of it. (link)

This, when combined with Sodium Thiosulfate (plain hypo), creates Farmer’ s Reducer. This is a reducer that dissolves away the silver that forms the image in a print. This results in the area of the print that has been treated becoming progressively lighter.

Bests,

David.
www.dsallen.de

Used in rehalogenating bleaches and cyanotypes as well...

 

[MDR]

Cyanotypes can be done with it the process allows for the use of either potassium hexacyanoferrate(II) (which this is) or the better choice potassium hexacyanoferrate(III) which is faster.

 

[railwayman3]

All the ferricyanide I've seen used in photography was a much deeper orange-red colour rather than yellow.

https://en.wikipedia.org/wiki/Potassium_ferricyanide gives a picture of this red compound and reference to several uses in photography.

https://en.wikipedia.org/wiki/Potassium_ferrocyanide shows the yellow compound, and has no reference to any photographic applications.

A random search for formulas for Farmers Reducer all seem to refer to the "ferri" compound.

 

[georg16nik]

Potassium Ferrocyanide is useful for latent image bleaching. e.g. on negatives it reduces highlight density, on positives it reduces the shadow density.

 

[railwayman3]

Potassium Ferrocyanide is useful for latent image bleaching. e.g. on negatives it reduces highlight density, on positives it reduces the shadow density.

If you google something like "ferrocyanide in image bleaching", all the references and formulae which come up are definitely using the "ferri" salt. Although the names are similar and confusing, they really are two totally different chemical compounds, not interchangeable. (I remember from college studies that the chemistry of the iron cyanides and similar compounds was head-achingly complicated!).

 

[georg16nik]

...indeed, I was thinking about “ferri” not “ferro” - my bad.

 

[Doremus Scudder]

Yes, ferrocyanide, the yellow stuff. As far as I know, it doesn't have any uses in photography, but then I saw an ebay listing for it from a seller who only sells photographic chemicals. So, am I missing something?

What does the seller say it's good for? Likely, he doesn't know and is mistaking this for "ferri." It seems pretty useless photographically to me...

Doremus

 

[Anon Ymous]

Thanks everyone. So, from MDR's response, it seems that the only use is as a suboptimal replacement for ferricyanide in cyanotypes.

What does the seller say it's good for? Likely, he doesn't know and is mistaking this for "ferri." It seems pretty useless photographically to me...

Doremus

To be honest, I only know few italian words. That said, google translate gives this:

Photography Potassium ferrocyanide has been used as a receiver for some processes using iron salts and as an additive for developers alkali (pyro)
It 'also used as a bleaching agent films
Laboratory reagent
analysis
Pigment (Prussian blue)
Industrial processes, metallurgy, oenology

Frankly, I don't know any developer, staining or not, that uses potassium ferrocyanide, or ferricyanide. Nor do I know of any bleach utilising it. I know it's used in wine making and as an anticaking agent, but that's all.

 

[Gerald C Koch]

I too think the seller is mistaking ferro for ferri. I can think of no uses for ferrocyanide in photography. I remember a few years ago when someone posted an offer to sell Glycin. Unfortunately what he had purchased was the amino acid glycine. What he had bought (IIRC a very large amount) was worthless as a developing agent. When dealing with chemicals the spelling of the names is very important. If possible check the CAS number. Each chemical has a unique number that correctly identifies it.

 

[railwayman3]

I can remember preparing "Prussian Blue" pigment in chemistry studies ( as in cyanotypes, etc., basically pot. ferricyanide and other iron compounds which I can't remember) and, very effectively, staining the bench,the floor, various utensils, my lab coat, shirt, trousers and fingers an attractive dark blue.

I didn't take up chemistry as a career.

 

[georgegrosu]

Ago 25-30 years the bleach at process for color negative ECN 2 you prepare from ferrocyanide and persulfate.
Ferrocyanide is yellow and and ferricyanide is orange.
For positive color process ECP 2 the bleaching you prepare from potassium ferricyanide.
http://motion.kodak.com/motion/uploadedFiles/h2407.pdf
„One gram of Potassium Ferricyanide (Anhydrous) can also be obtained by mixing 0.41 gram of potassium persulfate and 1.47 grams of sodium ferrocyanide decahydrate. The reaction between potassium persulfate and sodium ferrocyanide takes about 1 hour, after which the final adjust
ments to the mix should be made. The specific gravity of a bleach prepared by the reaction will be higher than when using the formula, and will get higher with each regeneration using potassium persulfate.”

George

 

[Sirius Glass]

Perhaps what you saw was Potassium Ferricyanide?

This, when combined with Sodium Thiosulfate (plain hypo), creates Farmer’ s Reducer. This is a reducer that dissolves away the silver that forms the image in a print. This results in the area of the print that has been treated becoming progressively lighter.

Bests,

David.
www.dsallen.de

Potassium Ferrocyanide is useful for latent image bleaching. e.g. on negatives it reduces highlight density, on positives it reduces the shadow density.

It can be used as part of the toning processes, but I usually use it to bleach the white areas to give the photograph more pop.

 

[Ian Grant]

The seller lists both Potassium Ferricyanide and Ferrocyanide, I've seen the Ferrocyanide used in old formulae.

Ian